This Month in Linebender, April 2025 (#105)

Co-authored-by: Olivier FAURE <[email protected]>
Co-authored-by: Taj Pereira <[email protected]>
Co-authored-by: Thomas Churchman <[email protected]>
Co-authored-by: Aaron Muir Hamilton <[email protected]>

Author: 5 people

content/blog/2025-05-07-tmil-16/android_view_voice_input.png

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+title = "Linebender in April 2025"
+authors = ["Daniel McNab", "Taj Pereira", "Tom Churchman"]
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+
+Linebender is an informal open-source organization working on various projects to advance the state of the art in GUI for [the Rust programming language](https://rust-lang.org).
+
+## RustWeek
+
+Many members of the Linebender community will be attending the [RustWeek 2025](https://rustweek.org/) conference, in Utrecht next month.
+At the time of writing, there are no longer tickets available, although there is a waitlist.
+Raph Levien will be giving a talk, titled [*Faster, easier 2D vector rendering*](https://rustweek.org/talks/raph/).
+This will be covering a lot of the sparse strips work discussed in [the Vello section](#vello).
+
+Matt Campbell will give a talk, titled [*AccessKit: reusable UI accessibility*](https://rustweek.org/talks/matt/).
+
+We will also be attending the [unconference](https://rustweek.org/unconf-intro/), as part of the "UI, App dev & Browser Summit" group.
+We're looking forward to working with other teams in the Rust UI ecosystem there.
+
+## Masonry
+
+Masonry is the widget system developed by Linebender.
+It provides a non-opinionated retained widget tree, designed as a base layer for high-level GUI frameworks.
+
+- [xilem#913][], [xilem#938][]: Ongoing work on properties, in preparation for adding more styling options.
+- [xilem#906][]: Improves Virtual Scrolling to support non-infinite use cases.
+- [xilem#922][]: Adds support for multiline text input, by alexjg.
+- [xilem#925][], [xilem#927][]: Update "line" scrolling to have a more correct speed, by Aaron Muir Hamilton and Alix Bott.
+- [xilem#929][]: Used trait upcasting to simplify how widgets use `Any`.
+- [xilem#937][]: Unifies test screenshots into a single folder, making it clearer which widget they relate to.
+
+<figure>
+<img style="height: auto" src="multiline_textbox.png" alt="To do list app, where the next item input says turn off the newline factory, with newlines before newline and factory. The final item also contains a newline." width="600" height="252">
+<figcaption>
+
+Masonry now has support for multi-line text inputs.
+
+</figcaption>
+</figure>
+
+## Xilem
+
+Xilem is our flagship GUI project, inspired by SwiftUI, which uses Masonry for its widgets.
+It lets you build user interfaces declaratively by composing lightweight views together, and will diff them to provide minimal updates to a retained layer.
+
+- [xilem#920][]: Slightly improves the handling of messages, using trait upcasting.
+- [xilem#921][]: Supports Masonry's virtual scrolling in Xilem.
+
+## Vello
+
+Vello is our GPU vector renderer.
+It can draw large 2D scenes with high performance, using GPU compute shaders for most of the work.
+
+- [vello#886][], [vello#887][]: Update the SDL2 example to SDL3.
+- [vello#892][]: Improved how our snapshot tests are handled in preparation for Kompari integration.
+
+Progress on the sparse strips renderers has also been continuing at pace.
+The big standout this month is the significant leap in Vello CPU functionality:
+
+- [vello#923][]: Blending, compositing, and layers.
+- [vello#893][]: Linear, radial and sweep gradients.
+- [vello#878][]: Clipping.
+- [vello#919][]: Image rendering.
+
+<figure>
+<img style="height: auto" src="cowboy.png" alt="Cowboy emoji, with a rainbox gradient mixed on top." width="300" height="300">
+<figcaption>
+
+An adapted version of Vello CPU's tests, showing support for blending, gradients and image rendering.
+
+</figcaption>
+</figure>
+
+The above PRs set the foundation for introducing these features into Vello Hybrid over the coming months.
+Another notable released feature is text outline rendering, which allows both renderers to draw text (emoji are not yet supported).
+
+- [vello#883][]: Text outline rendering for Vello CPU and Hybrid.
+- [vello#896][], [vello#897][]: Make the hinting robust, allowing clearer drawing in more cases.
+
+Our working roadmap can be found [here](https://docs.google.com/document/d/1ZquH-53j2OedTbgEKCJBKTh4WLE11UveM10mNdnVARY/edit?tab=t.0#heading=h.j3duh9pgdm94).
+This roadmap outlines our planned timeline for work on the renderers over the next year.
+
+## Parley
+
+Parley is a text layout library.
+It handles text layout, mostly at the level of line breaking and resolving glyph positions.
+
+- [parley#272][]: Added Kompari integration for testing into Parley.
+- [parley#315][]: Implemented properties based on CSS's `word-break` and `overflow-wrap`.
+- [parley#342][]: Fixes a bug in `align` where the offset wasn't being reset between calls.
+
+<figure>
+<img style="height: auto" src="break_all_second_half.png" alt="Text with a line break halfway through the word Antidisestablishmentarianism. The first characters after this break are underlined (indicating that those have the WordBreak property set)." width="626" height="408">
+<figcaption>
+
+[parley#315][] added the `WordBreak` style property, which is set to `BreakAll` on 'anism' in this screenshot.
+
+</figcaption>
+</figure>
+
+## Kurbo
+
+[Kurbo][] provides data structures and algorithms for curves and vector paths.
+
+We released [Kurbo 0.11.2][], adding the [`Triangle`][kurbo-triangle] shape, providing more ergomic methods on various shapes, and improving performance.
+The following are some highlights of this release.
+See the [changelog][Kurbo 0.11.2] for a full overview.
+
+- [kurbo#350][]: Adds the [`Triangle`][kurbo-triangle] shape.
+- [kurbo#383][]: Adds an efficient numerical method for approximating ellipse perimeters, originally described by Kummer (1837) and rediscovered by Linderholm and Segal (1995).
+- [kurbo#418][]: Adds `BezPath::with_capacity` to allow more efficient allocation if the size of the bezier path is known beforehand.
+- [kurbo#379][]: Adds some common derives to `Stroke` and `StrokeOpts`.
+- [kurbo#384][]: Implements `Div<f64>` and `Mul<f64>` for `Insets`.
+- [kurbo#399][], [kurbo#409][]: Implement `Sum` for `Vec2`, add `Vec2::turn_90` and `Vec2::rotate_scale`.
+- [kurbo#412][], [kurbo#413][]: Add `Size::{min,max}` and `Size::INFINITY`.
+- [kurbo#429][]: Adds `Affine::scale_about` and `Affine::then_scale_about`.
+- [kurbo#390][], [kurbo#428][]: Improve performance by reducing the number of operations in `Triangle::circumscribed_circle` and improving inlining.
+
+Multiple improvements to Kurbo are on the roadmap, such as improved stroke expansion in [kurbo#427][].
+
+## Color
+
+[Color][] provides functionality for representing, converting, parsing, serializing, and manipulating colors in a variety of color spaces.
+It closely follows the [CSS Color Module Level 4][] draft spec.
+
+We released [Color 0.3.0][], featuring the addition of manual chromatic adaptation and absolute color conversions, improved type conversion ergonomics, and more.
+This month saw the following changes, all included in the 0.3.0 release.
+See the [changelog][Color 0.3.0] for a full overview.
+
+- [color#156][], [color#164][], [color#165][]: Add specialized absolute color conversion methods for ProPhoto RGB, ACES2065-1 and ACEScg.
+  While `ColorSpace` includes default implementations for absolute color conversions, having these specializations improves computational efficiency.
+- [color#166][]: Uses faster (and [almost-correct][color-alphacolor-to-rgba8]) rounding for conversion from double precision floating point to 8-bit integer RGBA formats.
+  This works around slow x86 rounding behavior.
+- [color#155][]: Improves ergonomics by implementing `From<AlphaColor<_>> for DynamicColor` for all color spaces that have a `DynamicColor` counterpart.
+- [color#157][]: Removes the deprecated `From<Rgba8> for PremulColor<Srgb>` implementation.
+- [color#145][]: Fixes handling of powerless/missing components of the HWB color space, which is necessary for correct color interpolation when components are missing.
+- [color#158][], [color#159][]: Improve documentation for `DynamicColor::interpolate` and `gradient`, including usage examples.
+- [color#149][], [color#150][]: Improve constructing constant `Missing` flags and `Missing` documentation.
+
+## Android View
+
+[Android View](https://github.com/mwcampbell/android-view) is a platform integration for Rust code in Android apps.
+In April, Android View gained support for text input using the software keyboard, with accessibility support.
+
+<figure>
+<img style="height: auto" src="android_view_voice_input.png" alt="Android Screen, with text on the top half, and a keyboard visible with the word listening, followed by an ellipsis." width="252" height="257">
+<figcaption>
+
+Android View now allows many input methods on Android.
+This screenshot shows voice to text working in an app using Linebender libraries.
+This image has been edited to remove blank areas.
+
+</figcaption>
+</figure>
+
+## Research and Future Directions
+
+Linebender has an origin story in being a very research oriented group, looking to break new ground.
+While we are focused on shipping code today, we still have an eye on the future and how to be prepared for the new opportunities and technologies that are coming.
+
+Towards the end of April, some members of Linebender started working on ecosystem standardisation of input events, based on the web input events specification.
+This work is happening in the [UI Events](https://github.com/endoli/ui-events) repository.
+This is not a Linebender project, but we're watching it with great interest.
+
+We've also started thinking about how to make a renderer abstraction, allowing APIs which can use any of Vello's backends.
+The largest difficulty there is related to resources such as images.
+For example Vello Hybrid's image type would be a `wgpu` Texture, whereas Vello CPU should just use a heap-allocated buffer.
+We have some existing prototypes, see [#vello > Rendering abstraction prototype](https://xi.zulipchat.com/#narrow/channel/197075-vello/topic/Rendering.20abstraction.20prototype/with/516197002) for example.
+This work is likely to now continue after RustWeek.
+
+## Get Involved
+
+We welcome collaboration on any of our crates.
+This can include improving the documentation, implementing new features, improving our test coverage, or using them within your own code.
+
+We host an hour long office hours meeting each week where we discuss what's going on in our projects.
+See [#office hours in Zulip](https://xi.zulipchat.com/#narrow/channel/359642-office-hours) for details.
+We've also started a separate office hours time dedicated to the renderer collaboration, details also available at that link.
+
+- Daniel and Olivier's "office hours" appointments can still be booked by anyone for open-ended discussion of the ecosystem.
+  - [See Daniel's schedule here](https://calendar.google.com/calendar/u/0/appointments/schedules/AcZssZ32eQYJ9DtZ_wJaYNtT36YioETiloZDIdImFpBFRo5-XsqGzpikgkg47LPsiHhpiwiQ1orOwwW2).
+  - [See Olivier's schedule here](https://calendar.google.com/calendar/u/0/appointments/schedules/AcZssZ2t767ZRETD_TkRI_VxK2ZTG0VrO9OZ4l7HvTxefhtJcg85iK0ZN7zWNnAEZtH0Dn7C1GKxrmYM).
+
+[Kurbo]: https://docs.rs/kurbo/
+[kurbo-triangle]: https://docs.rs/kurbo/0.11.2/kurbo/struct.Triangle.html
+
+[Kurbo 0.11.2]: https://github.com/linebender/kurbo/releases/tag/v0.11.2
+
+[Color]: https://docs.rs/color/
+[CSS Color Module Level 4]: https://www.w3.org/TR/css-color-4/
+[color-alphacolor-to-rgba8]: https://docs.rs/color/0.3.0/color/struct.AlphaColor.html#method.to_rgba8
+
+[Color 0.3.0]: https://github.com/linebender/color/releases/tag/v0.3.0
+
+[color#145]: https://github.com/linebender/color/pull/145
+[color#149]: https://github.com/linebender/color/pull/149
+[color#150]: https://github.com/linebender/color/pull/150
+[color#155]: https://github.com/linebender/color/pull/155
+[color#156]: https://github.com/linebender/color/pull/156
+[color#157]: https://github.com/linebender/color/pull/157
+[color#158]: https://github.com/linebender/color/pull/158
+[color#159]: https://github.com/linebender/color/pull/159
+[color#164]: https://github.com/linebender/color/pull/164
+[color#165]: https://github.com/linebender/color/pull/165
+[color#166]: https://github.com/linebender/color/pull/166
+[kurbo#350]: https://github.com/linebender/kurbo/pull/350
+[kurbo#379]: https://github.com/linebender/kurbo/pull/379
+[kurbo#383]: https://github.com/linebender/kurbo/pull/383
+[kurbo#384]: https://github.com/linebender/kurbo/pull/384
+[kurbo#390]: https://github.com/linebender/kurbo/pull/390
+[kurbo#399]: https://github.com/linebender/kurbo/pull/399
+[kurbo#409]: https://github.com/linebender/kurbo/pull/409
+[kurbo#412]: https://github.com/linebender/kurbo/pull/412
+[kurbo#413]: https://github.com/linebender/kurbo/pull/413
+[kurbo#418]: https://github.com/linebender/kurbo/pull/418
+[kurbo#427]: https://github.com/linebender/kurbo/pull/427
+[kurbo#428]: https://github.com/linebender/kurbo/pull/428
+[kurbo#429]: https://github.com/linebender/kurbo/pull/429
+[parley#272]: https://github.com/linebender/parley/pull/272
+[parley#315]: https://github.com/linebender/parley/pull/315
+[parley#342]: https://github.com/linebender/parley/pull/342
+[vello#878]: https://github.com/linebender/vello/pull/878
+[vello#883]: https://github.com/linebender/vello/pull/883
+[vello#886]: https://github.com/linebender/vello/pull/886
+[vello#887]: https://github.com/linebender/vello/pull/887
+[vello#892]: https://github.com/linebender/vello/pull/892
+[vello#893]: https://github.com/linebender/vello/pull/893
+[vello#896]: https://github.com/linebender/vello/pull/896
+[vello#897]: https://github.com/linebender/vello/pull/897
+[vello#919]: https://github.com/linebender/vello/pull/919
+[vello#923]: https://github.com/linebender/vello/pull/923
+[xilem#906]: https://github.com/linebender/xilem/pull/906
+[xilem#913]: https://github.com/linebender/xilem/pull/913
+[xilem#920]: https://github.com/linebender/xilem/pull/920
+[xilem#921]: https://github.com/linebender/xilem/pull/921
+[xilem#922]: https://github.com/linebender/xilem/pull/922
+[xilem#925]: https://github.com/linebender/xilem/pull/925
+[xilem#927]: https://github.com/linebender/xilem/pull/927
+[xilem#929]: https://github.com/linebender/xilem/pull/929
+[xilem#937]: https://github.com/linebender/xilem/pull/937
+[xilem#938]: https://github.com/linebender/xilem/pull/938